From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 69D84C2D0DB for ; Thu, 23 Jan 2020 17:07:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DDF04214AF for ; Thu, 23 Jan 2020 17:07:37 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=cjr.nz header.i=@cjr.nz header.b="DZZmx/kh" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728900AbgAWRHh (ORCPT ); Thu, 23 Jan 2020 12:07:37 -0500 Received: from mx.cjr.nz ([51.158.111.142]:20888 "EHLO mx.cjr.nz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728803AbgAWRHh (ORCPT ); Thu, 23 Jan 2020 12:07:37 -0500 Received: from authenticated-user (mx.cjr.nz [51.158.111.142]) (Authenticated sender: pc) by mx.cjr.nz (Postfix) with ESMTPSA id 9E1C8808AB; Thu, 23 Jan 2020 17:07:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cjr.nz; s=dkim; t=1579799254; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=FdVKPe1ze00BBbcvbfyG5WKDkK7bMCGNVh8nJMtWX/Y=; b=DZZmx/khxl0bQS+2WnY6R2aelZhbJ9KpgCOv0Hp60TOY5gZUBblnJH/0F44AvLS9UGw3dh gDilb5NvCTd4zrxPtDDRsTx8AmkUC3BDA74R2vQvgjgE7aInMDqlvIIz+Aw5YXlhx7DC1b NL3T4+KfvneU/DADXS6sAxkjtXP6O0js+rAf9AoxF+P8pJO2J4bm22akqMebBJpXgN6Yz8 6qmluN6nSm20bNqRXG91ZVsyBmfzepXIJBuvJWTsISmWr8SzzCB10JYRy1D//g7+DAy0lU P74a2dldEkbEamius5N2jepU4TJdqDuoeNZYsgwgVkoCIhS/KuqkeDdLdo9a0w== From: Paulo Alcantara To: Vincent Whitchurch , sfrench@samba.org Cc: linux-cifs@vger.kernel.org, kernel@axis.com, Vincent Whitchurch Subject: Re: [PATCH] CIFS: Fix task struct use-after-free on reconnect In-Reply-To: <20200123160906.28498-1-vincent.whitchurch@axis.com> References: <20200123160906.28498-1-vincent.whitchurch@axis.com> Date: Thu, 23 Jan 2020 14:07:28 -0300 Message-ID: <87lfpyyucv.fsf@cjr.nz> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-cifs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-cifs@vger.kernel.org Vincent Whitchurch writes: > The task which created the MID may be gone by the time cifsd attempts to > call the callbacks on MIDs from cifs_reconnect(). > > This leads to a use-after-free of the task struct in cifs_wake_up_task: > > ================================================================== > BUG: KASAN: use-after-free in __lock_acquire+0x31a0/0x3270 > Read of size 8 at addr ffff8880103e3a68 by task cifsd/630 > > CPU: 0 PID: 630 Comm: cifsd Not tainted 5.5.0-rc6+ #119 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014 > Call Trace: > dump_stack+0x8e/0xcb > print_address_description.constprop.5+0x1d3/0x3c0 > ? __lock_acquire+0x31a0/0x3270 > __kasan_report+0x152/0x1aa > ? __lock_acquire+0x31a0/0x3270 > ? __lock_acquire+0x31a0/0x3270 > kasan_report+0xe/0x20 > __lock_acquire+0x31a0/0x3270 > ? __wake_up_common+0x1dc/0x630 > ? _raw_spin_unlock_irqrestore+0x4c/0x60 > ? mark_held_locks+0xf0/0xf0 > ? _raw_spin_unlock_irqrestore+0x39/0x60 > ? __wake_up_common_lock+0xd5/0x130 > ? __wake_up_common+0x630/0x630 > lock_acquire+0x13f/0x330 > ? try_to_wake_up+0xa3/0x19e0 > _raw_spin_lock_irqsave+0x38/0x50 > ? try_to_wake_up+0xa3/0x19e0 > try_to_wake_up+0xa3/0x19e0 > ? cifs_compound_callback+0x178/0x210 > ? set_cpus_allowed_ptr+0x10/0x10 > cifs_reconnect+0xa1c/0x15d0 > ? generic_ip_connect+0x1860/0x1860 > ? rwlock_bug.part.0+0x90/0x90 > cifs_readv_from_socket+0x479/0x690 > cifs_read_from_socket+0x9d/0xe0 > ? cifs_readv_from_socket+0x690/0x690 > ? mempool_resize+0x690/0x690 > ? rwlock_bug.part.0+0x90/0x90 > ? memset+0x1f/0x40 > ? allocate_buffers+0xff/0x340 > cifs_demultiplex_thread+0x388/0x2a50 > ? cifs_handle_standard+0x610/0x610 > ? rcu_read_lock_held_common+0x120/0x120 > ? mark_lock+0x11b/0xc00 > ? __lock_acquire+0x14ed/0x3270 > ? __kthread_parkme+0x78/0x100 > ? lockdep_hardirqs_on+0x3e8/0x560 > ? lock_downgrade+0x6a0/0x6a0 > ? lockdep_hardirqs_on+0x3e8/0x560 > ? _raw_spin_unlock_irqrestore+0x39/0x60 > ? cifs_handle_standard+0x610/0x610 > kthread+0x2bb/0x3a0 > ? kthread_create_worker_on_cpu+0xc0/0xc0 > ret_from_fork+0x3a/0x50 > > Allocated by task 649: > save_stack+0x19/0x70 > __kasan_kmalloc.constprop.5+0xa6/0xf0 > kmem_cache_alloc+0x107/0x320 > copy_process+0x17bc/0x5370 > _do_fork+0x103/0xbf0 > __x64_sys_clone+0x168/0x1e0 > do_syscall_64+0x9b/0xec0 > entry_SYSCALL_64_after_hwframe+0x49/0xbe > > Freed by task 0: > save_stack+0x19/0x70 > __kasan_slab_free+0x11d/0x160 > kmem_cache_free+0xb5/0x3d0 > rcu_core+0x52f/0x1230 > __do_softirq+0x24d/0x962 > > The buggy address belongs to the object at ffff8880103e32c0 > which belongs to the cache task_struct of size 6016 > The buggy address is located 1960 bytes inside of > 6016-byte region [ffff8880103e32c0, ffff8880103e4a40) > The buggy address belongs to the page: > page:ffffea000040f800 refcount:1 mapcount:0 mapping:ffff8880108da5c0 > index:0xffff8880103e4c00 compound_mapcount: 0 > raw: 4000000000010200 ffffea00001f2208 ffffea00001e3408 ffff8880108da5c0 > raw: ffff8880103e4c00 0000000000050003 00000001ffffffff 0000000000000000 > page dumped because: kasan: bad access detected > > Memory state around the buggy address: > ffff8880103e3900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > ffff8880103e3980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > >ffff8880103e3a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > ^ > ffff8880103e3a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > ffff8880103e3b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > ================================================================== > > This can be reliably reproduced by adding the below delay to > cifs_reconnect(), running find(1) on the mount, restarting the samba > server while find is running, and killing find during the delay: > > spin_unlock(&GlobalMid_Lock); > mutex_unlock(&server->srv_mutex); > > + msleep(10000); > + > cifs_dbg(FYI, "%s: issuing mid callbacks\n", __func__); > list_for_each_safe(tmp, tmp2, &retry_list) { > mid_entry = list_entry(tmp, struct mid_q_entry, qhead); > > Fix this by holding a reference to the task struct until the MID is > freed. > > Signed-off-by: Vincent Whitchurch > --- > fs/cifs/cifsglob.h | 1 + > fs/cifs/smb2transport.c | 2 ++ > fs/cifs/transport.c | 3 +++ > 3 files changed, 6 insertions(+) Reviewed-by: Paulo Alcantara (SUSE) Thanks, Paulo